I am on FMLA and have been accused of abusing FMLA for vacations and personal use by my supervisor

Hello,

I have been on intermediate fmla since May of this year for my knee when I have flare ups that require me to miss work. I recently have had more flare ups than usual and was called into a meeting with HR and my supervisor. I was accused of using fmla for vacations, going to the beach and things not related to my injury which is NOT true. I know several of my colleagues have been upset with my condition and that they have to work extra when I am out and feel like they made up these scenarios out of jealousy. I am extremely frustrated and they do not have any evidence of this. I feel as though my condition was used again me and now I am being harassed by my supervisor. Any advice on how to handle this?